120 
 WTNT44 KNHC 290232
 TCDAT4
  
 TROPICAL STORM DON DISCUSSION NUMBER   6
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042011
 1000 PM CDT THU JUL 28 2011
  
 BOTH NOAA AND AIR FORCE RECONNAISSANCE PLANES HAVE BEEN
 INVESTIGATING TROPICAL STORM DON AND FOUND THAT THE CYCLONE HAD
 JOGGED TO THE WEST DURING THE PAST FEW HOURS AND THAT THE CYCLONE
 IS A LITTLE BIT STRONGER. THE MINIMUM CENTRAL PRESSURES REPORTED BY
 NOAA AND AIR FORCE PLANE EARLIER THIS EVENING WERE 996 AND 998
 RESPECTIVELY. MORE RECENTLY A HIGHER PRESSURE WAS REPORTED BUT THE
 DROPSONDE DID NOT HIT THE VERY SMALL CENTER. SATELLITE INTENSITY
 ESTIMATES FROM TAFB AND SAB HAVE INCREASED TO 3.0 AND 3.5 ON THE
 DVORAK SCALE. THE INITIAL HAS BEEN INCREASED TO 45 KNOTS PRIMARILY
 BASED ON A BELIEVABLE 43-KNOT SFMR REPORT. THE CYCLONE HAS BEEN
 UNDER THE INFLUENCE OF NORTHERLY SHEAR AND THE LOW-LEVEL CENTER IS
 STILL TILTED SOUTHWARD WITH HEIGHT AS REPORTED BY BOTH PLANES.
 SINCE NO SIGNIFICANT DECREASE OF THE SHEAR IS ANTICIPATED AND THE
 CYCLONE IS INTERACTING WITH DRY AIR OVER THE WESTERN GULF OF
 MEXICO...ONLY A SMALL AMOUNT OF STRENGTHENING IS FORECAST BEFORE
 LANDFALL. IN FACT NONE OF THE GUIDANCE SUGGEST IMPORTANT CHANGES IN
 INTENSITY.    
 
 DURING THE PAST FEW HOURS...DON HAS BEEN MOVING BETWEEN THE WEST AND 
 WEST-NORTHWEST AT 12 KNOTS. A STRONG HIGH PRESSURE SYSTEM OVER THE
 SOUTHERN UNITED STATES HAS BEEN CONTROLLING THE TRACK OF THE
 CYCLONE. SINCE THIS HIGH IS FORECAST BY MOST OF THE GLOBAL MODELS
 TO PERSIST...A CONTINUATION OF A GENERALLY WEST-NORTHWESTWARD TRACK 
 IS ANTICIPATED UNTIL LANDFALL. THE OFFICIAL TRACK HAS BEEN SHIFTED
 SOUTHWARD A LITTLE BIT AND THIS DUE TO THE INITIAL WESTWARD JOG AND
 NOT DUE TO ANY IMPORTANT CHANGE IN THE STEERING PATTERN. GIVEN THE
 SMALL SOUTHWARD SHIFT OF THE TRACK...THE TROPICAL STORM WATCH FOR
 THE SOUTHERN TEXAS COAST HAS BEEN REPLACED WITH A TROPICAL STORM
 WARNING. 
 
 INTERESTS IN EXTREME NORTHEAST MEXICO SHOULD CLOSELY MONITOR THE
 PROGRESS OF DON. AN UNEXPECTED SMALL DEVIATION TO THE SOUTH OF THE
 TRACK COULD NECESSITATE THE ISSUANCE OF WARNINGS FOR THE EXTREME
 NORTHEASTERN COAST OF MEXICO.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  29/0300Z 24.7N  92.5W   45 KT  50 MPH
  12H  29/1200Z 25.5N  94.3W   50 KT  60 MPH
  24H  30/0000Z 26.6N  96.6W   55 KT  65 MPH
  36H  30/1200Z 27.5N  99.0W   30 KT  35 MPH...INLAND
  48H  31/0000Z 28.5N 101.5W   25 KT  30 MPH...INLAND
  72H  01/0000Z...DISSIPATED
  
 $$
 FORECASTER AVILA
  
 

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